scsi: ch: remove ch_mutex()

ch_mutex() was introduced with a mechanical conversion, but as we now have
correct locking we can remove it altogether.

Link: https://lore.kernel.org/r/20200213153207.123357-4-hare@suse.deReviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ch.c

@@ -44,7 +44,6 @@ MODULE_LICENSE("GPL");
 MODULE_ALIAS_CHARDEV_MAJOR(SCSI_CHANGER_MAJOR);
 MODULE_ALIAS_SCSI_DEVICE(TYPE_MEDIUM_CHANGER);
 
-static DEFINE_MUTEX(ch_mutex);
 static int init = 1;
 module_param(init, int, 0444);
 MODULE_PARM_DESC(init, \
@@ -591,26 +590,22 @@ ch_open(struct inode *inode, struct file *file)
 	scsi_changer *ch;
 	int minor = iminor(inode);
 
-	mutex_lock(&ch_mutex);
 	spin_lock(&ch_index_lock);
 	ch = idr_find(&ch_index_idr, minor);
 
 	if (ch == NULL || !kref_get_unless_zero(&ch->ref)) {
 		spin_unlock(&ch_index_lock);
-		mutex_unlock(&ch_mutex);
 		return -ENXIO;
 	}
 	spin_unlock(&ch_index_lock);
 	if (scsi_device_get(ch->device)) {
 		kref_put(&ch->ref, ch_destroy);
-		mutex_unlock(&ch_mutex);
 		return -ENXIO;
 	}
 	/* Synchronize with ch_probe() */
 	mutex_lock(&ch->lock);
 	file->private_data = ch;
 	mutex_unlock(&ch->lock);
-	mutex_unlock(&ch_mutex);
 	return 0;
 }